A wide variety of nucleotide compositions and nucleotide analog compositions have been provided for use in a variety of different applications. In some cases, these compositions function as analytical reagents for the analysis of biological processes, e.g., in nucleic acid sequencing reactions. In other cases, these compositions function as pharmaceutically active substances for the treatment of disease. In still other aspects, these compositions form building blocks for other commercial applications. In a number of situations, a basic nucleotide, e.g., a nucleoside triphosphate, is coupled to an additional functional group in order to provide an additional or a different function to that compound. For example, in one of the more ubiquitous embodiments, detectable label groups, such as fluorescent dyes, radiolabels, semiconductor nanocrystals, or the like, are coupled to the nucleotide to render the nucleotide more easily detectable, e.g., through a fluorescent microscope. These labels may be coupled to persistent components of the nucleotide, i.e., the nucleobase, that remains even following polymerization with other nucleotides, or they may be coupled through the transient portions, e.g., a gamma phosphate group that may be removed upon polymerization. In other cases, functional groups may be coupled to nucleotides or nucleotide analogs in order to provide therapeutic activity, e.g., in interrupting viral replication, or the like.
Despite the widespread use of functionally tagged nucleotides, it would be desirable to provide for a modular nucleotide composition that allows simple and flexible functionalization of nucleotides for use in a variety of different applications. The present invention meets these and other needs.